1. Field of the Invention
This invention relates to a positive resist composition which responds to radiations such as ultraviolet ray, far ultraviolet rays including excimer laser and the like, electron beam, ion beam, X ray and the like.
2. Related Art
Recently, with a rise in the integration level of integrated circuits, formation of patterns of sub-micron order is required, and it is desired to provide a positive resist composition which is excellent in various properties such as a profile, a depth of focus and resolution. In particular, for the production of 16-64M DRAMs, it is required to resolve a pattern having a line width of 0.5 .mu.m or less with a good profile and a broad depth of focus.
In SPIE Vol. 1086, Advances in Resist Technology and Processing VI (1989)/Pages 363-373, there are mentioned positive resist compositions comprising cresol/formaldehyde novolak resin and a triester obtained through a condensation reaction of naphthoquinone-2-diazide-5-sulfonic acid with each of 2,3,4-trihydroxybenzophenone, 2,6-bis[(2-hydroxy-3,5-dimethylphenyl)methyl]-4-methylphenol and 2,6-bis[( 4-hydroxy-3,5-dimethylphenyl)-methyl]-4methylphenol.
In Japanese Patent Application KOKAI No. 2-285351, there is mentioned a positive photoresist composition comprising an alkali-soluble novolac resin and a photosensitive material obtainable by reacting a polyhydroxy compound having in one molecule at least one group represented by the following formula: ##STR3## wherein R.sup.1 and R.sup.2 each represent hydrogen atom or a straight chain or branched chain alkyl or alkoxy group having 1-4 carbon atoms provided that R.sup.1 and R.sup.2 cannot simultaneously be hydrogen atom, and 1,2-naphthoquinone-5-(and/or -4-) sulfonyl chloride. In Japanese Patent Application KOKAI No. 2-296249, there is mentioned a positive resist composition comprising an alkali-soluble phenolic resin and a photosensitive material containing a quinonediazidesulfonate of a compound represented by the following formula: ##STR4## wherein R.sup.1 to R.sup.5 each represent hydrogen atom, halogen atom, alkyl, alkenyl or alkoxy group having 1-4 carbon atoms or hydroxyl group provided that at least one of R.sup.1 to R.sup.5 is a group of the following formula: ##STR5## wherein R.sup.6 and R.sup.7 each represent halogen atom, alkyl group or alkenyl group and n represents 0, 1 or 2. Further, in Japanese Patent Application KOKAI No. 62-10646, there is mentioned a positive photoresist composition comprising an alkali-soluble phenolic resin and a photosensitive material containing a condensation product of a phenol compound represented by the following formula: ##STR6## wherein R.sup.2 to R.sup.3 each represent hydrogen atom or lower alkyl group, with o-quinonediazidesulfonyl chloride. Further, in Japanese Patent Application KOKAI No. 2-296248, there is mentioned a positive resist composition comprising an alkali-soluble phenolic resin and, as a photosensitive material, a quinonediazidesulfonate represented by the following formula: ##STR7## wherein R.sup.1 to R.sup.5 each represent hydrogen atom, halogen atom, C.sub.1 -C.sub.4 alkyl, alkenyl or alkoxy, or hydroxyl group, provided that at least one of R.sup.1 to R.sup.5 is a group of the following formula: ##STR8## and A represents --S--, --O--, --C(O)--, --C(O)--O--, --S(O)--, --(O)S(O)-- or --C(R.sup.7)(R.sup.8)-- wherein R.sup.6 represents halogen atom, alkyl group or alkenyl group, R.sup.7 and R.sup.8 each represent hydrogen atom, alkyl group, alkenyl group or phenyl group, and n represents 0, 1 or 2.
None of these composition, however, have been able to resolve a pattern having a line width of 0.5 .mu.m or less with a broad depth of focus and with a good profile.